MODELING PROFILES AND SIGNATURES OF ENRICHMENTS

Abstract:

Anthropogenic and geochemical enrichment of soils and living matter have been well documented ^{1, 2, 3.}

Here we report on geochemical, anthropogenic and biological enrichments with heavy metals in Modern Peru and compared this to Modern and ancient data from New Mexico, USA.

We established a signature derived from the quantities of 25 metals in various biological, fossil and soil materials. We also speculate that human adaptation to mercury toxicity may occur in remarkably short time spans during the Holocene.

We found mercury concentrations in Modern pigeon feathers and llama wool from free foraging birds and animals in Albuquerque, NM, ranging from 0.006 to 0.019 mg/Kg of tissue. The values for Modern Peru ranged from 22.0 to 556 mg/Kg for the same tissues. We discovered, in 64 million-year-old fossilized plants from New Mexico (Paleocene Nacimiento Formation, San Juan Basin), a mercury concentration of 1.11 mg/Kg of fossil, whereas Modern plant material from the Rio Grande Basin in New Mexico contained no mercury.

Profiling of metal content of these samples suggests that mercury is a proxy for anthropogenic rather than geochemical enrichment in the localities we examined.

We found no overt signs of mercury toxicity in contemporaneous inhabitants of Huancavelica⁴, Peru; one of the ten most mercury-polluted places in the world and the mercury concentration in their hair is well below modern admissible levels. However, assessment of their annual scalp hair growth-rate showed marked reduction in growth (~ 5cm/yr) versus ~ 16cm/year for normal scalp hair from other continents⁴. This is consistent with a toxic effect of heavy metals on human metabolism and especially autonomic nervous system function in Huancavelica, Peru.

Contemporaneous anthropogenic activities are known to increase heavy metal content in the biosphere with potentially toxic effects on humans. However, signs of human evolutionary adaptation to such toxins might already be evident in Peru⁴.